1. Field of the Invention
The present invention relates to an original contents creation apparatus, a derived contents creation apparatus, a derived contents using apparatus, an original contents creation method, a derived contents creation method, and derived contents using method and verification method.
2. Description of the Related Art
In a contents distribution system on the Internet, it is necessary to protect contents from unauthorized use and tamper. As such a technology for protecting the contents, for example, disclosed has been a technology for protecting the contents by integrating the contents and a use rule together as a package, and then to make a digital signature on the package and encode the package concerned (for example, refer to Japanese Patent Publication No. H10-512074 (published in 1998)). However, such an existing contents protection technology is on the premise of end-to-end protection, and has eliminated an addition of secondary contents on a distribution path between an original contents provider and an end user.
In the field of broadcasting, a model is established, in which a local station purchases original contents provided by a key station, and inserts an advertisement suitable for a region covered by the local station. This model has a merit for the key station in that it becomes easy to recover an expense of producing the original contents by effective use thereof, and has a merit for the local station in that an increase of advertisement income can be expected by redistributing the high-quality contents produced by the key station.
It is conceivable that a similar model to the above is realized in contents distribution on the Internet to expand a use range of the original contents, thus making it possible to contribute to an expansion of profit resources of an original contents provider and to a service improvement of a secondary provider. A contents distribution system that permits the secondary provider to add the secondary contents is hereinafter referred to as a “derived contents distribution system”.
As an aspect of realizing the derived contents distribution system, there is a model of completely entrusting the secondary provider to add the secondary contents and protect the derived contents. In this model, the secondary provider acquires the original contents through a safe communication path, adds the secondary contents thereto, and then gives an appropriate protection to derived contents thus formed, and distributes the contents concerned to the end user. This model is premised on a complete relationship of trust between the original contents provider and the secondary contents provider, and is established only when it is reliable that the secondary provider abides by a condition to be met by the secondary contents and a condition to protect the original contents, and so on.
From a viewpoint of expanding the use of the contents, desirable is a derived contents distribution system that permits the insertion of the secondary contents not only by the specific reliable secondary provider but also by any number of secondary providers. However, establishing the relationship of trust, which is as described above, with any number of secondary providers lacks in scalability. Moreover, when unauthorized derived contents or contents that are not appropriately protected are distributed, it becomes difficult to pursue a secondary provider causing such an inappropriate distribution.
Meanwhile, the secondary provider requires a function to prevent the secondary contents from being removed from the derived contents in an unauthorized manner. For example, such a situation must be avoided, where advertisement contents and a sponsor name, which are added as the secondary contents, are deleted on the distribution path, and the user can watch and listen to only the original contents.
Further, in regard to the contents, there is disclosed a method for setting a limitation rule to add a control over the use of the contents (for example, refer to Japanese Patent No. 3485911). However, in this method, it is difficult to perform a correctness verification of the modified contents (the secondary contents) and the limitation rule.